1. Field of the Invention
The present invention relates to a relay apparatus which relays a signal between an image forming device and a post-processing device which have different interfaces, and an image forming system including the relay apparatus.
2. Description of Related Art
To a subsequent stage of an image forming device which prints out an image by forming the image on a sheet, one or a plurality of post-processing devices having each function to perform processing such as punching, stitching, and folding, and to bundle a plurality of sheets to create a brochure are connected in series. Thereby, an image forming system is configured.
In such an image forming system, various types of information are exchanged between the image forming device and the post-processing device in order to match various sheet conditions (sheet size, paper type, and basis weight) or post-processing conditions. For example, the information is exchanged in the following sequences.
At the timing of feeding a sheet from a sheet feeding unit of the image forming device, the image forming device notifies the post-processing device of the sheet feed information including the sheet information relating to the above sheet and the post-processing information indicating the contents of post-processing to be performed for the above sheet. Based on the notified sheet feed information, each post-processing device calculates time necessary for the post-processing in the post-processing device and time corresponding to a sheet interval, and notifies the image forming device of the above calculated time. The image forming device allows the fed sheet to stand by at a predetermined standby position provided on the way to a carrier path, and releases a standby state to discharge the sheet at the timing corresponding to the time notified by the post-processing device. By this control, a sheet interval necessary for the post-processing device is secured.
FIG. 23 shows a connection example in the case where an image forming device and a plurality of post-processing devices are connected in series through serial interfaces (I/F) of the same communication system (protocol). In such a connection state, the information is sent in order from upstream to downstream (image forming device→post-processing device 1→post-processing device 2→post-processing device 3) or from downstream to upstream, and the information is sequentially transmitted. In Japanese Patent Application Publication No. 2007-210775, for example, a technique in which the information relating to jam generated on a downstream side is sequentially sent to an upstream device is disclosed. Further, in Japanese Patent Application Publication No. 2009-83449, a technique in which log data on the downstream side is sequentially sent to an upstream device is disclosed.
FIG. 24 shows a specific example in the case where sheet feed information is notified through the above-described sequence in the image forming system shown in FIG. 23. In this example, there is shown a communication sequence in which a punch process is performed in the post-processing device 1, a sheet is carried by a bypass conveyance in the post-processing device 2 (a sheet is carried to a subsequent-stage post-processing device without performing post-processing), and a side stitching process is performed in the post-processing device 3 to create two sets of brochures each of which has two sheets.
Every when one sheet is fed, the image forming device outputs sheet feed information (sheet information and post-processing information) relating to a sheet to be fed and carried to the subsequent-stage post-processing devices. The sheet feed information is transmitted in order from the image forming device to the post-processing device 1→the post-processing device 2→the post-processing device 3. In FIG. 24, a suffix added to each piece of information indicates that the sheet number of the sheet corresponding to the information and the set number of the set including the above sheet. To be more specific, “1-1”, “1-2”, “2-1”, and “2-2” indicate a first sheet of a first set, a second sheet of the first set, a first sheet of a second set, and a second sheet of the second set, respectively.
Based on the received sheet feed information, each post-processing device calculates time of a sheet interval necessary for post-processing (time for allowing a sheet to stand by in the image forming device). Then, each post-processing device notifies wait information indicating the calculated time in the order of the post-processing device 3→the post-processing device 2→the post-processing device 1→the image forming device to notify the image forming device of the wait information. The wait information is sent back for each piece of sheet feed information (for each sheet). For example, the wait information 2-1 indicates a sheet interval between the second sheet of the first set and the first sheet of the second set.
By stopping a sheet temporarily at a standby position according to the time indicated by the wait information notified from the post-processing device, the image forming device secures the time (sheet interval) necessary for the post-processing device. For example, the standby time at the standby position in the image forming device (timing for releasing the standby state) is controlled so as to set the time until the first sheet of the second set is discharged (output timing of the sheet discharge information 2-1) after the second sheet of the first set is discharged (output timing of the sheet discharge information 1-2), to the time indicated by the wait information 2-1. In addition, the sheet discharge information is notified to a subsequent-stage device in accordance with the timing at which a sheet is discharged from each device.
In recent years, a post-processing device of the image forming system has been diversified into various kinds. The demand in which not only a post-processing device of a manufacturer which manufactures an image forming device but also a post-processing device of a different manufacturer (hereinafter, referred to as a third vendor) is connected and operated on line, has been increased.
On the other hand, with regard to the connection of the post-processing device in the image forming system, each communication specification for exchanging information is not standardized and unified.
In this background, it is inefficient that each third vendor is compliant with complicated interface specifications of a manufacturer which manufactures the image forming device. To solve the above problem, a parallel interface is adopted as a simple interface which is common to each third vendor. It is not necessary for a third vendor to be conscious of the interface specification of a manufacturer of the image forming device main body and the interface specification of each manufacturer, and a post-processing device can be developed and provided by using only a simple interface.
Further, as shown in FIG. 25, the following image forming device is proposed (see Japanese Patent Application Publication No. 2006-350961). In the image forming device, both a serial interface and a parallel interface are provided, and a post-processing device (genuine device) which is compliant with the serial interface and a post-processing device (third vendor device) which is compliant with the parallel interface can be connected.
In case that a post-processing device (genuine device) which is compliant with a serial interface a manufacturer of an image forming device and a post-processing device (third vendor device) which is compliant with a parallel interface are mixed to configure an image forming system, because a number of combinations of types of devices to be connected and the number of the devices to be connected are considered, it is difficult for the image forming device to have interfaces for all post-processing devices and to handle all connection patterns.
For example, in case of the image forming device which has a serial interface of a communication protocol in which the above-described sheet feed information is transmitted to a post-processing device and a sheet interval (wait information) necessary for the post-processing device is acquired from the post-processing device as a response of the transmitted sheet feed information and which adjusts a standby time at a standby position so as to discharge a sheet at the timing indicated by the acquired wait information, when a third vendor device which is compliant with a simple parallel interface is connected to the above image forming device, the information necessary for the control of carrying the sheet cannot be acquired from the third vendor device. Therefore, it is difficult that the image forming device is operated so as to discharge a sheet in accordance with a sheet interval necessary for the third vendor device. Further, when the number of types of the third vendor device to be connected is increased, it is very troublesome that the necessary functions are added to the image forming device so as to handle all the third vendor devices.
Further, because the heights at which the carrier inlet and the carrier outlet for the sheets are disposed from the installation surface are also different from each other depending on the third vendor devices, it is required to adjust the above heights in order to connect the third vendor device to the image forming system and carry the sheet.
In addition, in the parallel interface, the amount of information to be exchanged is very small as compared to the serial interface. Therefore, it is difficult to manage the control of carrying the sheets according to the types of the sheets (sheet size, paper type, and basis weight), which is performed in the genuine device having the serial interface. For example, in case of the control of the sheet interval, the control of the sheet interval cannot be performed according to the types of sheets and the above control is performed under worst conditions. As a result, the problem in which the productivity of the system is lowered, has been caused.